What should you do when the people you thought to be your friends treat you like you're not there...?

How is that I always start a friendship with people and I almost always end up being hurt. It starts out great but after a while they just start getting bored of me. I don't bluff, I know when to keep my mouth shut, I know when to leave people alone, I am always there for them in their lowest points but it's like the only way people get to respect you is when you are a total *** and when you have a lot to say and with a bit of evilish qualities. should I just start being on my own or keep on trying. 19 years old and I don't have one good friend. They always manipulate me and once they're done using me and get what they want (most of the time material stuff) they go back to ignoring me. I am the smarter of all the cliques I've ever been in, I never feel that inflated about it or even acknowledge it (actually they are the ones who always keep on reminding me that I am so smart) Could that be the reason why they always end up turning their backs on me.